Lijie Hao

Observation of re-entrant spin reorientation in TbFe 1− x Mn x O 3

We report a spin reorientation from Γ4(Gx, Ay, Fz) to Γ1(Ax, Gy, Cz) magnetic configuration near room temperature and a re-entrant transition from Γ1(Ax, Gy, Cz) to Γ4(Gx, Ay, Fz) at low temperature in TbFe1−xMnxO3 single crystals by performing both magnetization and neutron diffraction measurements. The Γ4 − Γ1 spin reorientation temperature can be enhanced to room temperature when x is around 0.5 ~ 0.6. These new transitions are distinct from the well-known Γ4 − Γ2 transition observed in TbFeO3, and the sinusoidal antiferromagnetism to complex spiral magnetism transition observed in multiferroic TbMnO3. We further study the evolution of magnetic entropy change (−ΔSM) versus Mn concentration to reveal the mechanism of the re-entrant spin reorientation behavior and the complex magnetic phase at low temperature. The variation of −ΔSM between a and c axes indicates the significant change of magnetocrystalline anisotropy energy in the TbFe1−xMnxO3 system. Furthermore, as Jahn-Teller inactive Fe3+ ions coexist with Jahn-Teller active Mn3+ ions, various anisotropy interactions, compete with each other, giving rise to a rich magnetic phase diagram. The large magnetocaloric effect reveals that the studied material could be a potential magnetic refrigerant. These findings expand our knowledge of spin reorientation phenomena and offer the alternative realization of spin-switching devices at room temperature in the rare-earth orthoferrites.

Crystal growth and phase diagram of 112-type iron pnictide superconductor Ca1−y La y Fe1−x Ni x As2

We report a systematic crystal growth and characterization of Ca1−y La y Fe1−x Ni x As2, the newly discovered 112-type iron-based superconductor. After substituting Fe by a small amount of Ni, bulk superconductivity is successfully obtained in high-quality single crystals sized up to 6 mm. Resistivity measurements indicate common features for transport properties in this 112-type iron pnictide, suggest strong scattering from chemical dopants. Together with the superconducting transition temperature T c , and the Neel temperature T N determined by the elastic neutron scattering, we sketch a three-dimensional phase diagram in the combination of both Ni and La dopings.

Effects of Co Substitution on the Magnetic Excitation in Heavy Fermion Compound PrFe4P12

We performed measurements of specific heat and inelastic neutron scattering on Pr(Fe1-xCox)4P12 to investigate the effects of d-electron doping on the heavy fermion (HF) state and non-magnetic order state of PrFe4P12. The ordered state is suppressed by the Co substitution. A Schottky type behavior in the specific-heat appears at 8 K, in contrast with the undoped system. The inelastic neutron spectrum of the Co substituted system is composed of several sharp inelastic peaks, in contrast with the quasi-elastic spectrum in the HF phase of PrFe4P12. The experimental results indicate that the Co substitution induces localized 4f electrons of Pr ions with suppression of the HF state and the exotic ordering.